The present invention relates to a tube pulling apparatus and more particularly to a tube pulling apparatus which is adapted to pull tubes from a tube sheet of heat exchangers, condensers and the like. This application is a continuation of my prior U.S. patent application Ser. No. 09/161,639 filed Sep. 28, 1998 entitled Tube Pulling Apparatus.
In condensers, boilers, and heat exchangers where two fluids are brought into thermal communication, it is customary to pass one fluid through a plurality of tubes and to pass the other fluid around the exterior of the tubes. The fluid passing around the exterior of the tubes is contained in the shell of the heat exchanger. In most constructions, the tubes are spaced apart and separated from the fluid in the shell by two end plates commonly known as tube sheets. Each tube sheet contains a plurality of holes into which the tubes are inserted. The tubes extend between the tube sheets so that a fluid-tight barrier is formed between the two fluids. To anchor each tube in its respective hole in the tube sheet, the end of the tube is expanded and flared.
It is customary to replace heat exchanger tubes after they have become corroded and pitted and when they commence leaking fluid across the barrier. In replacing tubes, it is common to hydraulically extract the old tubes from the tube sheet and replace them with new tubes.
Hydraulically-operated tube pullers are well known and generally include a tubular housing placed in abutment with a tube sheet so that a gripping member projecting therefrom will be received within the tube to be extracted. The gripping member is radially expanded into biting engagement with the internal surface of the tube by a wedging element. A first piston, which is connected to the wedging element, moves the wedging element relative to the gripping member to effect its expansion. The first piston cooperates with a second piston, which is connected to the gripping member, to conjointly retract the wedging element and the gripping member, resulting in the extraction of the tube from the tube sheet.
Prior art patents for tube pullers can be seen in the Martin U.S. Pat. No. 4,959,899, for a tube pulling device for extracting a tube from a tube sheet in heat exchangers, condensers, and the like and has a shaft for expanding the gripping jaws of a tube puller and a second shaft for pulling the gripped tube. Each of the two shafts is hydraulically actuated. In the Armstrong, Jr. U.S. Pat. No. 4,369,569, a tube pulling apparatus is provided which pulls tubes from tube sheets of heat exchangers, condensers, and similar equipment and hydraulically actuates one shaft that actuates the gripping jaws and which shaft is driven by a first piston. Once the gripping jaws are fully expanded, the first piston cooperates with the second piston which is connected to the gripping jaws to extract the expansion rod and the gripping jaws to extract the tube. The Smith U.S. Pat. No. 4,077,102, shows another tube extracting mechanism for extracting tubes from a tube sheet and which compensates for variations due to manufacturing tolerances in the inside diameters of the tubes being extracted from the sheet.
In the Ciminero U.S. Pat. No. 4,000,556, a method and apparatus for extracting tubes from heat exchangers simultaneously pulls a pair of sliding wedging jaws within a tube to be extracted while extracting the tube. The Somerville U.S. Pat. No. 5,159,743, is a hydraulic puller having a base assembly about a central axis and a camming assembly about the base assembly and a readily removable hydraulic module axially centered in the base assembly to allow for a convenient assembly and disassembly of the hydraulic puller unit. The Beard U.S. Pat. No. 5,208,967, is a tube extraction apparatus for tubes and the like suitable for removing condenser and heat exchanger tubes from their mountings in electrical power generation systems. The Keys U.S. Pat. No. 3,791,011, is a tube pulling device for pulling tubes from a tube sheet in heat exchangers, condensers and the like and has an inner piston connected to a tube gripping means for initially gripping the inside of the tube when fluid pressure is applied to the inner piston. An outer piston is exposed through an open port means from the hydraulic fluid at the time of the gripping of the tube. In the Filer U.S. Pat. No. 4,213,239, a tube extractor utilizes a fluid pressure activated broach which is expanded and drawn into the end of the tube without expanding the outside diameter of the tube which then withdraws the tube from the tube sheet. The Miller U.S. Pat. No. 4,283,826, is a tube extracting mechanism for extracting tubes from a tube sheet and includes an expansion hydraulic cylinder for imparting longitudinal movement to a mandrel and then pulling hydraulic cylinders for imparting longitudinal movement to a sleeve and expandable jaw. The Mancabelli U.S. Pat. No. 4,627,155, is a tube extracting apparatus having a pulling shaft connected to a gripping assembly for gripping the tube.
The present invention is an improvement to the operation of a tube extracting apparatus which utilizes a first shaft for gripping the inner part of a tube and a second pulling shaft for pulling the tube. The shafts interconnect with a spool valve for first activating the gripping jaws to grip the inside of a tube to be pulled and then activating a pulling shaft to pull the tube from a tube sheet of a heat exchanger or condenser.